This invention relates generally to shipboard systems, and more particularly to improvements in systems for distribution of electrical signals representing parameters such as heading, roll, pitch and heave to various shipboard systems which utilize the signals. The invention has particular utility in ocean bottom mapping by means of sonar.
Ocean bottom mapping is typically carried out by means of a wide swath array sonar system in which arrays of transmitting transducers (projectors) and receiving transducers (hydrophones) are provided on the underside of the hull of a ship. Typically, the projectors and hydrophones are disposed along perpendicular lines. U.S. Pat. No. 5,077,699, by A. J. Passamante et al., describes a wide swath bottom mapping system in which an array of sonic projectors extends in the fore and aft direction and projects a fan-shaped sonic beam toward the ocean floor. An array of hydrophones, which extends athwartships, is used to receive the echoes of the projected beams, and the signals from the hydrophones are digitally processed to produce a map of the contour of the bottom of a body of water.
In any continuously operated sonar bottom mapping system, it is important to keep track of the ship's heave (the vertical movement of the ship) to make corrections in the data gathered by the sonar system. In a bottom mapping system using orthogonally disposed transmitting and receiving arrays, it is also necessary to keep track of, and make corrections for, pitch, roll and heading, since the gathered data will be affected by these parameters.
Pitch, roll and heading information is ordinarily generated by several redundant systems. Typically the ship is equipped with two Miniature Ship's Inertial Navigation Systems (MINISINS), which are accurate dead reckoning devices utilizing inertial measurement units comprising x and y velocity meters on a gyro-stabilized platform. The x and y velocity meters sense the ship's motion and produce outputs which are converted into computer format by multiplexed encoder circuits in a navigation control console. Changes in the ships heading, and pitching and rolling movements of the ship, manifest themselves as changes in the signals produced by the x and y velocity meters. A computer calculates angular data based- upon the velocity data. The angular data is then used to equalize the platform and is also supplied as outputs representing pitch, roll and heading. These outputs are in the form of polyphase alternating current signals usable by a synchro receiver.
The ship is also typically equipped with a gyrocompass composed of a three-axis, gimbaled platform having synchros on the gimbals to measure platform angles. The platform angles determine pitch, roll and heading, which are also provided as polyphase alternating current signals usable by a synchro receiver.
Heave information is provided by a heave sensing accelerometer, and is converted into vertical displacement by a heave processor, the output of which is in digital form.
Pitch, roll, heading and heave information is utilized by various shipboard systems.
For example, on a ship in which the array of hydrophones extends athwartships, roll data is utilized by a receiver/translator control unit, which sets the gain, bandwidth, sampling delay and sample number for a triple channel acoustic receiver and dual base band translator which provide all of the timing functions for the system. The control unit collects the reflection data sampled by the receiver and combines the reflection data with a sample identifying number and roll data corresponding to the ship's roll at the time the reflection was received.
Pitch data is utilized by a pitch compensator, which provides three signals to be utilized by a pitch resolver. One signal initiates a transmit pulse causes the projectors to operate. Another signal signifies whether the apparatus is operating in a shallow or deep mode. Still another signal controls the phase offset, signal delay and power level for each of the amplifiers which drive the projectors.
In the case in which the projectors are athwartships and the hydrophone array extends in the fore and aft direction, the roll and pitch data may be interchanged.
Heading information is utilized by a current profiler system, which develops and records a velocity profile of the water currents beneath the ship and provides sonar-derived velocity data, including fore-aft, athwartships and vertical components, to a navigation computer. Heading information is also provided to a synchro amplifier, which distributes heading data to various heading indicators, including mission heading indicators, a chart room heading indicator and pilot house heading indicators.
The roll, pitch and heading information is utilized by the receiver/translator control unit, pitch compensator, current profiler and synchro amplifier in the form of polyphase, alternating current, synchro signals.
Roll, pitch and heading data are also utilized, in digital form along with heave data, by a sonar communication computer, a narrow beam sonar system and a navigation computer. The sonar communication computer supplies output ping control data to the transmitting, receiving and test equipment sections of the sonar system, and supplies time-tagged attitude, velocity measurement, status and alarm data to a sonar computer. The narrow beam sonar system provides a single-beam, conventional source of sonar depth data. It is usually operated simultaneously with the wide swath array sonar system to verify proper operation of the latter, and can be used as the primary source of depth data whenever the wide swath array sonar system is not operating. The navigation computer receives inputs from several sensor systems in addition to the roll, pitch, heading and heave data. The data received by the navigation computer is used to determine the ship's "best present position" in terms of latitude and longitude, and the ship's velocity. The navigation computer provides ship's velocity in terms of velocity components in North-South, East-West, fore-aft, port-starboard, and vertical directions.
Ships' attitude data systems previously in use, utilized a large number of manually operable, rotary switches to control the distribution of attitude data throughout the shipboard system. The switching equipment required a large amount of space, and was complex and difficult to operate. To distribute data from a selected source to the various destinations, it was necessary to rotate numerous switches to their proper positions. The procedure was error-prone, since an inadvertent misadjustment of any of the many switches would result in a system discrepancy for example transmission of data from two sources simultaneously.
Another problem with the prior ships' attitude data systems was that they were capable of providing only static simulations. A device known as a "dummy director" was provided to generate synchro signals representing simulated values of roll pitch and heading. The dummy director was a three channel, dual speed digital-to-synchro converters with three thumbwheel switches for selecting values of roll, pitch and heading respectively. The device was used with the complex switching equipment described above, and, unless the rotary switches were operated properly, it was possible to mix simulation signals with actual roll, pitch and heading signals and thereby produce errors.
The principal object of this invention is to provide an improved ship's attitude data system having a simpler and more reliable switching system. Another object is to provide for the elimination of errors resulting from the inadvertent switching of data from multiple sources. Still another object of the invention is to provide a ship's attitude data system in which dynamic simulations of roll, pitch and heading data can be distributed both in analog and digital form simultaneously.